The 3' end of each telomere is a single-stranded overhang of repeats of TTAGGG that is proposed to help form a loop structure at the chromosome ends. Considerable evidence suggests the exposure of the telomere overhang occurs by experimental disruption, DNA damage or progressive telomere shortening. This exposure can be mimicked by adding small DNA oligonucleotides homologous to the telomere 3' overhang as a signal for DNA damage responses such as apoptosis. To explore the mechanism and possible therapeutic utility of this response we designed an 11-base oligonucleotide homologous to the telomere overhang for studies on apoptosis in melanoma described below. Aims: (1) Study the role of p73, E2F1 and Rb on the apoptotic response induced by the telomere overhang DNA. (2) Examine the decrease of anti-apoptotic protein livin and activation of caspases by telomere overhang DNA. (3) Study the induction by the telomere overhang sequence of markers of melanocyte differentiation such as Mart-1/Melan A, Tyrosinase, gp100, TRP-1 and TRP-2 in melanoma cells. (4) Investigate whether these oligonucleotides will reduce the number of metastatic nodules and size of tumors in SCID mice. The modulation and regulation of the various proteins will be studied by Western blotting. Analysis of apoptosis will be done on the FACS scan and all transfections will be performed by lipofectamine plus and analysed by Western blotting. Significance: The above project will study the mechanism and utility of these oligonucleotides to induce apoptosis in vivo and in vitro and its effect on tumodgenecity and metastasis of tumors.The high rate of metastasis contributes greatly to the pathogenesis of melanoma and are major causes of death among melanoma patients. The project will facilitate the development of these telomere based DNA-damage mimetic oligonucleotides as a novel anti-cancer therapy.